If we traveled 100 light years into space, would we really see the Earth as it was 100 years ago?

Yes, but you might not be able to see enough details for you to actually tell you were seeing it in the past.

From the Earth, Apollo astronauts on the Moon had a 1.3 second delay before receiving radio signals from Earth. The Earth was always 1.3 seconds in their past. Similarly, if you were out at 100 light years, any Earth signal you received, would have been emitted from Earth 100 years in your past, so in essence, you would always see the Earth as it was 100 years in your past.

Copyright 1997 Dr. Sten Odenwald